Process and apparatus for dialyzing solutions



J. ZENDER Nov. 19, 1946.

PROCESS AND APPARATUS FOR DIALYZING SOLUTIONS ZSheets-Sheet 1 Filed July8, 1943 Ill nnnnnn I INVENTOR.

B JUST! ZENDER like.

Patentecl- N... 1c, 1946 STATES PATENT time amass PROCESS ANDAPPARA'IUSFOR DIALY ZING SOLUTIONS Justin Zender, Fredericksburg, Va.-, assignorto Sylvania Industrial Corporation, Fredericksburg, Va., a corporationof Virginia Application July 8, 1943, Serial No. 493,918

.sheets must be maintained under pressure or firmly sealed to avoid lossof liquid during dialysis. To clean the apparatus or to replace a broken7 Claims. (Cl. 210-85) In the now preferred embodiment the apparatuscomprises a. chamber having headers disposed transversely adjacent eachend to divide the chamber into three separate compartments,

tubular dialyzing membranes connected at each end to the headers andcommunicating with a common liquid compartment, and means for passing afluid around the tubes in the central compartment.

sheet, it is generally necessary to completely dismantle the dialyzer.Further, to decrease breakage, the membranes must be supported overtheir surfaces. Finally, such prior apparatus did not provide any 'meansfor retarding the dilution of the solution being dialyzed. Thus, sheetdialyzers of prior design have generally been complicated inconstruction, difficult to repair orto clean and capable of handlingonly small volumes of liquid.

Accordingly, it is a general object of the present invention to providea dialyzer which will be capable of handling large volumes of liquid andwhich will operate rapidly.

It is a further general object to provide a dialyzing apparatus which iseasy to construct and to'clean and in which broken membranes may bereplaced without completely dismantling the dialyzer.

It is another object of the invention to provide a process for theseparation of water-soluble substances from their aqueous solutions in arapid and efficient manner, and in particular for the separation ofproducts of fermentation from the fermented liquor.

A specific object is to provide an-apparatus having means for retardingthe dilution of the solution being dialyzed.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

According to the present invention, there is provided an apparatus forthe dialysis of solutions comprising, in combination, a chamber, a.multiplicity of tubular dialyzing membranes disposed therein, means topass the solution to be dialyzed into contact with one surface of thetube, means to pass another liquid into contact with the other surfaceof the tube, and preferably means to continuously concentrate thesolution bein dialyzed so as to increase the rate of dialysis.

In the following specifications and in the appended claims, the termdialyzate will be used to designate the solution being dialyzed inaccordance with recent usage in the art; the term diffusate willdesignate the solution of the material which diffuses through themembrane during dialysis, and the term dialysis will be used todesignate the diffusion of soluble substances through a semi-permeablemembrane from one liquid into another. 4 The invention accordinglycomprises the features of construction, combinations of elements, andarrangement of parts which willbe exemplified in the constructionhereinafter set forth and the scope of the invention will be indicatedin the claims.

For a more complete understanding of the nature and objects of theinvention, reference should be had to the accompanying drawings in whichFig. 1 represents a side elevation, partly in sec- Fig. 4 is a sideelevation, partly. in section, of

the dialyzer of the invention utilizing a, double tube;

Fig. 5 is a top plan view, in section, of the-apparatus of Fig. 4 takenalong the line 55 there.. of and Figure 6 is a top plan view in sectionof-the apparatus .of Figure 4 taken along the line 6-6 thereof.

In that embodiment of the apparatus shown in Figs. 1 and 2, thedialyzing chamber proper comprises a vertical outer chamber 10, which isshown as a cylindrical chamber, but which may be of any cross-sectionalshape. The chamber is closed at the top by a removable plate II, and isclosed at the bottom by a conical base [2, which is provided with adrain I3 having a valve l4.

"I8. there are positioned headers I8 and 16, each provided with aplurality of holes. Short sections of pipe H are threaded into theupperheader I and similar sections of pipe 22 are threaded into 5 the lowerheader I6, These pipes serve to anchor the dialysis tubes I8 to theheaders. C

The chamber- H] is provided with a removable side portion 38 which makesthe interior accessible from the outside. When it is desired to 10change or replace a tube, the apparatus is drained, the bolts 39removed, and the side portion 38 of the chamber and the plate I I takenout. The upper end of the tube is then pulled through the section ofpipe l'L and the end turned down over the upper end of the pipe H toform I the cuff 23. The band 24, which may b formed of rubber, as shown,or of metal or the like, is

then slipped over the cut? 23, anchoring it securely to the pipe IT. Aband24' similar to the, band 24 is then slipped over the free lower endof the tube I8, and the end of the tube inserted over the upper end ofthe lower pipe 22'. The band 24' is'then slipped down over the end ofthe tube I8, anchoring it securely to the pipe 22. 25

The coupling shown in Fig. 1 has the advantage of maintaining themaximum diameter of the tube I8 at the joint, and thus does notinterfere with the flow of the liquid through the tube I8.

The dialysis tubes I8 may be disposed and 'arranged within the chamberI0 in any desired manner, in rows, for example, or in concentric circlesas shown in Fig. 2. The space between the tubes can be varied asdesired, but in general a distance of the order of /2 to 1 inch issumcient. It is to be understood that a space exists around all of thetubes illustrated in Fig. 2, and that none of these tubes are indirectcontact with each other along their longitudinal surfaces.

It is to be understood that the apparatus shown in Fig. 1 may beconstructed and arranged so that the dialyzate may be caused to passinside the tubes or outside the tubes, but for the purpose ofillustration only, the apparatus of Fig, 1

is constructed and arranged so that the 'dialyzate can be introducedinto the lower section 25 of a the chamber I8 by means of the pipe 28,the dialyzate filling the lower section of the pipe upward through theinterior of the tubes I8-and filling the upper section 21 until itoverflows through the outlet 28. The diflusate will be 111-.troducedinto the intermediate chamber 29 ata the top through the pipe 38and will be removed at the bottom through the pipe 3|. It is to beunderstood that the circulation of the dialyzate and/or of the diffusatemay be continuous or intermittent. When it is desired to clean theapparatus, the dialyzate may be drained off through the exhaust pipe I3which is positioned at the lowermost point of the bottom section 25.

It should be noted that the present apparatus is so constructed that thedialy zing tubes I8 are completely submerged in liquid so that noportion isin contact withthe air. This is a desirable feature since ithas been found that cer- 85' tainmembranes, particularly those formed ofnon-fibrous cellulosic materials, are attacked by certain bacteria ororganisms found in fermented sugar solutions and molasses resulting inthe rapid deterioration of .themembrane. This ac- 7 tion is avoided orsubstantially retarded when the'm'embranes are completely submerged inthe liquid, and precautions are taken to avoid introducing bubbles ofair in either of ,the liquids.

' It'is also to be understood that th apparatus of -.4 the invention canbe arranged without transcending the scope of the invention so as toprovide thatthe dialyzate and the difi'usate both flow upward ordownward in the same direction instead of flowing countercurrent to eachother as shown in Fig.1.

Further, the apparatus of the type shown in 1 may be so readily modifiedby anyone skilled in the art, without transcending the scope which has ahigher specificgravity than the diffusate, the tubes will tend to floatso that they can be kept in position merely by suitable guide pins. i

There is also shown in Figs. 3, 4, 5 and 6 another embodiment of theapparatus of the inven-- tion in which the dialyzing tubes are double ormultiwalled. Referring to Fig. 3, this-embodiment comprises. an innerdialyzing tube I811.

surrounded by a dialyzing tube I8b of larger diameter, and, ifnecessary, supported externally.

by means of a textile tube I8c made of an open mesh fabric whether ofwoven, knitted, or braided construction. The surrounding outer dialyzingtube IN: is particularly advantageous when-it is desired to concentratethe dialyzate while it is being subjected simultaneously to dialysis.Thus a plurality of the tubes illustrated in Fig, 3 may be supportedbetween the headers a shown' in the apparatus of Fig. 4, leaving an airspace'35 between the tubes. The side walls of the chamber 35.are solidas shown in the figure. However,. there are no front and back walls tothe chamber 35, as is fully brought out in Figure 5. Thus it is possibleto blow air through the chamber 35 across the outer surface of the tubeI8c, thus causing an evaporation of liquid through the wall of the tubeI8b, as shown in Figure 5.

Positioning the double tubes in the chamber Illa requires the use ofdouble headers at'the.

top andbottom of the chamber. Accordingly. the outer tubes I 8b and Iare afilxed to the inner headers I5a and Ilia, while the inner tube I8ais afiixed to the lowermost header I5 and the uppermost header It. Inthis embodiment, it'is preferable to have the dialyzate occupy the spacebetween the tubes 18a and I'8b, and to have the diifusate occupy thespace in the interior of the tube I8a. Accordin ly. referring to Fig.'4, the dialyzate is introduced into the lower section 25a through theinlet tube 26a so that it fills the pipe 30a, whereupon it fills thissection and flows down through the interior of the tube I 8a and fillsthe lower section 81 from which it passes through the exit tube 3| a.

' Since the front and back walls of the chamber v35 are open, ltlis asimple matter to aflix the tubes I81) and I8c to'the header IIa. Inorder to provide access to the inner tubes I841 in the chamber 25a-andto the upper parts of the outer tubes I8b and I8c in the chamber2'Ia'and the upper part of the innertubes I8a, and. the chem ber 36,removable front portions are provided in the walls of the chambers. Atypical construcwhen the tube tion oi the walls of each of thesechambers is shown in Figure 6 which represents a crosssectional view ofthe chamber 25a taken along the line 6-6 of Figure 4. The removablefront wall portion 45 is ailixed to the apparatus wall Illa by means ofthe bolts 41. Similar removable wall portions are provided inchambe'rs'Zla and 36.

During the operation ofthe apparatus shown in Figs. 4 and 5, the solublesubstances are caused to difiuse from the layer of dialyzate whichpasses in the space between the tubes l 8a and lb into the diifusatewhich is flowing terior of the tube ma. Simultaneously, water or solventfrom the diffusate will be flowing through the tube l8a into thedialyzate thus diluting the through the inthe wet gel state, i, e.,while they are swollen rate a hydrophilic organic liquid from water ororganic compounds of a difierent type there may be employed tubes formedof hydrophobic coldialyzate. If the procedure of dilution is notretarded, it will result in the slowing down of the process of dialysis,the rate of which depends upon the difference in concentration of thesoluble' material between the dialyzate and the diffusate. Thus,according to one embodiment of the present invention, air is blown overthe outside of the multiwalled tube so that water is continuouslyevaporated from the diffusate through the wall lab and through the openmesh fabric iBc. It has been found, for example, that Iilb is formed ofregenerated cellulose and the diffusate is an aqueous solvent, the rateof evaporation of water through the regenerated cellulose tube I812 isthe same as the rate of evaporation from the same solution contained ina bath. In other words, the rate of evaporation appears to beindependent of the membranes. This appears to be due to the fact thatthe water diffuses in the wall of the tube I81; and evaporates from itsexternal surface. Thus, the present invention provides a process andapparatus by which the dialysis can be carried' out simultaneously withthe concentration of the dialyzate so that the decrease in the rate ofdialysis resulting from dilution of the diilusate can be substantiallyretarded or prevented.

' Preferably, the air which is caused to flow over the tube |8c is'airheated to an elevated temperature of the boiling point of Water, butpreferably between 50 and 60 F. The heat transferred to the dialyzate isthus advantageous in preventing further fermentation and increasing therate of dialysis. Any conventional air blower and air heater may beemployed.

For treating aqueous liquid compositions, the tubes I8, I81: and l 8b'may be formed of any hydrophilic film-forming material, such,forexample, as parchment paper, tubes made from leather waste as soldunder the trade names Brechtee and Naturin and tubes made from anyfilm-forming non-fibrous oellulosic materials as a class. ,For thetreatment of aqueous fluid compositions where it is desired to cause thediffusion and separation of water or water-miscible organic compoundsfrom inorganic or organic sub,- stances whether liquid or solids, thereis preferably employed a hydrophilic cellulosic tube such,

for example, as one formed of regenerated cellulose or cellulose hydratewhich has been produced by regeneration from viscose or' from solutionsof cellulose in inorganic or organic solvents or from cuprammoniumcellulose or by the deesterification of cellulose'esters such as, by thedenitrationof cellulose nitrate, also membranes formed ofalkali-soluble, water-insoluble cellulose ethers, gelatine(insolubilized), casein, al-

ginates, and the like film-forming hydrophilic' plastic materials. Suchtubes are employed'in the entire apparatus.

philic tubing. Accordingly, the

serves a four-fold purpose:

loidal materials as a class of which there may be given by way ofexample, tubes formed of of a hydrophobicresin with a hydrophobiccellulose derivative. When hydrophobic tubes are employed they arepreferably used in the swollen gel state, i. e., while they aresaturated with the organic liquid which it is desired toevaporatethrough the tube.

The present apparatus is adapted for dialyzing both organic andinorganic substances from organic or aqueous solutions. On the one hand,organic substances may be separated from aqueous or non-aqueous.organic; solutions by use of a semi-permeable hydrophobic tubing, whileon the other hand water-soluble substances maybe separated from aqueoussolutions by use of a hydropresent apparatus may be used for separatinginorganic or organic crystalloids from their solutions, or forseparating crystalloids from colloids, or for separating inorganicsubstances from organic substances, or for separating organic liquidsfrom aqueous or non-aqueous solutions. In particular, the apparatus isapplicable for the separation of glycerine, butylene glycol, citricacid, sugar and inorganic salts and the like, from their aqueoussolutions.

.The heating of the dialyzate from to 100 C. (a) to continuouslyconcentrate the dialyzate since water is evaporated in the evaporator;(b) to increase the rate of dialysis; (c) to eliminate dissolved air andair bubbles; (d) to sterilize the dialyzate and prevent furtherfermentation.

The apparatus has many advantages, namely, the dialyzing membranes beingin the form of a tube are more self-supporting than fl-at sheets andthey can-be readily anchored at each end without danger of leaks. When atube breaks, the liquid may be quickly drained from the apparatus and atube replaced without dismantling Since the tubes are not constricted atthe entrance or exit where they are joined to the headers, the flow ofliquid therethrough is not retarded and there is no. tendency forsediment to collect inside the tube; further, a rapid flow can bemaintained through the tubes.

-Thus, there is provided a means for continuously concentrating thedialyzate while preventing the process and in the constructions setforth, which embody the invention, may be made without departing fromits scope, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secureby Letter Patentis:

1. An apparatus for the dialysis of solutions comprising, incombination, a chamber, a multiplicity of tubular dialyzing membranescomprising outer tubes of relatively large diameter and tubes ofrelatively small diameter, disposed in said tubes of large diameter,means spaced within said chamber supporting said tubular dialyzingmembranes, means to pass the solution to be dialyzed through the outertube into contact with onesurface of the inner tube, means to passanotherliquid through the inner tube into contact with the other surfaceof the inner tube, and means to continuously concentrate the solution.

being dialyzed so as to increase the rate of dialysis.

2. An apparatus for the dialysis of solutionsfor the outer tubecomprising an open mesh fabric, disposed therein, means spaced'withinsaid chamber supporting said tubular dialyzing membranes, means to passthe solution to be dialyzed through the outer tube into contact with onesurface of the-inner tube, means to pass another liquid into contactwith the other surface of the inner tube, and means to continuouslyconcentrate the solution being dialyzed so as to increase the rate ofdialysis.

3. An apparatus for thedialysis of solutions comprising, in combination,a chamber having inner and outer headers disposed transversely adjacenteach end and defining a space between them, dialyzing membranes in theform of inner and outer concentric tubes of different diameters disposedin said space and connected at each end to said headers, the inner tubebeing connected to the outer headers and the outer tube 8, i beingconnected to the inner headers, means to pass a solution throughtheinner tube, means to pass a diiferent solution through the .spacebetween the inner and the outer tube, and

insJanS to pass a. fluid on the outside of the outer 4. An apparatusaccording to claim 3 in which there is provided means for passing airover the surface of the outer dialyzer tube so as to evaporate liquidfrom the surface of said tube.

5. A process for the dialysis of solutions comprising passing thesolution to be dialyzed into contact with one surface of a dialyzingmembrane in the form of a tube, passing another liq? uid into contactwith the other surface of said tube, and continuously concentrating thesolution being dialyzed at a point spaced from the di alyzing membrane,and continuously recirculating the concentrated solution, whereby theconcentration gradient between the dialyzate and the difiusate ismaintained at its-highest level throughout the dialysis process.

6. A process for dialyzing solutions comprising passing the solution tobe dialyzed through an outer tubular dialyzer, in contact with an innertubular dialyzer which is concentric with the first tubular dialyzer,passing another liquid through and in contact with the inner tubulardialyzer, and passing air over theexternal surface of the outer tubulardialyzer whereby a liquid is caused to be evaporated from said dialyzer.

7. A process for dialyzing solutions comprising passing the solution tobe dialyzed through a tubular dialyzer of relatively large diameter incontact with tubular dialyzer of smaller diameter which is disposedinside said larger tubular dialyzer, passing another liquid through andin contact with the tubular dialyzer of smaller diameter, and passing athird fluid over the external surface ofithe. larger tubular dialyzer.

JUSTIN ZENDER.

